A pro rata assessment plan insurer has power at any time to reclassify, transfer, or rearrange its members, to merge or unite circles or groups; and to unite into one (1) group or circle two (2) or more groups or circles, the membership of which has decreased below the maximum. The insurer shall not start a new group or circle so long as any other group or circle is not up to maximum. All groups and circles shall be kept up to the maximum.